381 research outputs found
Coherent π^0 photoproduction on the deuteron up to 4 GeV
The differential cross section for ^2H(γ,d)π^0 has been measured at deuteron center-of-mass angles of 90° and 136°. This work reports the first data for this reaction above a photon energy of 1 GeV, and permits a test of the apparent constituent counting rule and reduced nuclear amplitude behavior as observed in elastic ed scattering. Measurements were performed up to a photon energy of 4.0 GeV, and are in good agreement with previous lower energy measurements. Overall, the data are inconsistent with both constituent-counting rule and reduced nuclear amplitude predictions
First Measurement of the Helicity Asymmetry E in Æž Photoproduction on the Proton
Results are presented for the first measurement of the double-polarization helicity asymmetry E for the ƞ photoproduction reaction ɣp -\u3e ηp. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the Jülich-Bonn model to examine the case for the existence of a narrow N* resonance between 1.66 and 1.70 GeV. The addition of these data to the world database results in marked changes in the predictions for the Eobservable from that model. Further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances
Assessment of bulbar function in amyotrophic lateral sclerosis: validation of a self-report scale (Center for Neurologic Study Bulbar Function Scale).
BACKGROUND AND PURPOSE: Impaired bulbar functions of speech and swallowing are among the most serious consequences of amyotrophic lateral sclerosis (ALS). Despite this, clinical trials in ALS have rarely emphasized bulbar function as an endpoint. The rater-administered Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) or various quality-of-life measures are commonly used to measure symptomatic benefit. Accordingly, we sought to evaluate the utility of measures specific to bulbar function in ALS.
METHODS: We assessed bulbar functions in 120 patients with ALS, with clinicians first making direct observations of the degree of speech, swallowing and salivation impairment in these subjects. Clinical diagnosis of bulbar impairment was then compared with ALSFRS-R scores, speech rate, time to swallow liquids and solids, and scores obtained when patients completed visual analog scales (VASs) and the newly-developed 21-question self-administered Center for Neurologic Study Bulbar Function Scale (CNS-BFS).
RESULTS: The CNS-BFS, ALSFRS-R, VAS and timed speech and swallowing were all concordant with clinician diagnosis. The self-report CNS-BFS and ALSFRS-R bulbar subscale best predicted clinician diagnosis with misclassification rates of 8% and 14% at the optimal cut-offs, respectively. In addition, the CNS-BFS speech and swallowing subscales outperformed both the bulbar component of the ALSFRS-R and speech and swallowing VASs when correlations were made between these scales and objective measures of timed reading and swallowing.
CONCLUSIONS: Based on these findings and its relative ease of administration, we conclude that the CNS-BFS is a useful metric for assessing bulbar function in patients with ALS
Determination of the pion charge form factor for Q^2=0.60-1.60 GeV^2
The data analysis for the reaction H(e,e' pi^+)n, which was used to determine
values for the charged pion form factor Fpi for values of Q^2=0.6-1.6 GeV^2,
has been repeated with careful inspection of all steps and special attention to
systematic uncertainties. Also the method used to extract Fpi from the measured
longitudinal cross section was critically reconsidered. Final values for the
separated longitudinal and transverse cross sections and the extracted values
of Fpi are presented.Comment: 11 pages, 6 figure
Separated Kaon Electroproduction Cross Section and the Kaon Form Factor from 6 GeV JLab Data
The () reaction was studied as a function of
the Mandelstam variable using data from the E01-004 (FPI-2) and E93-018
experiments that were carried out in Hall C at the 6 GeV Jefferson Lab. The
cross section was fully separated into longitudinal and transverse components,
and two interference terms at four-momentum transfers of 1.00, 1.36 and
2.07 GeV. The kaon form factor was extracted from the longitudinal cross
section using the Regge model by Vanderhaeghen, Guidal, and Laget. The results
establish the method, previously used successfully for pion analyses, for
extracting the kaon form factor. Data from 12 GeV Jefferson Lab experiments are
expected to have sufficient precision to distinguish between theoretical
predictions, for example recent perturbative QCD calculations with modern
parton distribution amplitudes. The leading-twist behavior for light mesons is
predicted to set in for values of between 5-10 GeV, which makes data
in the few GeV regime particularly interesting. The dependence at fixed
and of the longitudinal cross section we extracted seems consistent
with the QCD factorization prediction within the experimental uncertainty
Inclusive Electron-Nucleus Scattering at Large Momentum Transfer
Inclusive electron scattering is measured with 4.045 GeV incident beam energy
from C, Fe and Au targets. The measured energy transfers and angles correspond
to a kinematic range for Bjorken and momentum transfers from . When analyzed in terms of the y-scaling function the data show
for the first time an approach to scaling for values of the initial nucleon
momenta significantly greater than the nuclear matter Fermi-momentum (i.e. GeV/c).Comment: 5 pages TEX, 5 Postscript figures also available at
http://www.krl.caltech.edu/preprints/OAP.htm
Measurement of the Charged Pion Electromagnetic Form Factor
Separated longitudinal and transverse structure functions for the reaction
1H(e,eprime pi+)n were measured in the momentum transfer region Q2=0.6-1.6
(GeV/c)**2 at a value of the invariant mass W=1.95 GeV. New values for the pion
charge form factor were extracted from the longitudinal cross section by using
a recently developed Regge model. The results indicate that the pion form
factor in this region is larger than previously assumed and is consistent with
a monopole parameterization fitted to very low Q2 elastic data.Comment: 5 pages, 3 figure
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